1. Field of the Invention
The invention relates to a mobile telephone unit, more particularly to an apparatus which permits hands-free operation of a mobile telephone unit in a car.
2. Description of the Related Art
It is known that driving while holding a mobile telephone unit on one hand can increase the risk of vehicular accidents. FIG. 1 illustrates a known apparatus 10 which permits hand-free operation of a mobile telephone unit (T) in a car, thereby permitting the driver of the car to drive and use the mobile telephone unit (T) at the same time. The apparatus 10 comprises a main terminal 11, a plug 12 adapted to be inserted into a cigarette lighter socket of a car, a microphone 13, a loudspeaker 14 and a telephone connector 15. The main terminal 11 is to be secured within the passenger room of the car. The plug 12 is connected to the main terminal 11 via an electrical cable 121 and serves to connect electrically the main terminal 11 to the car battery, thereby providing electrical power to the apparatus 10. The telephone connector 15 is connected to the main terminal 11 via an electrical cable 151 and serves to connect electrically the mobile telephone unit (T) to the main terminal 11 so that wireless incoming signals received by the mobile telephone unit (T) can be received by the main terminal 11 and so that wireless outgoing signals from the main terminal 11 can be sent to the mobile telephone unit (T) so as to be transmitted wirelessly by the latter. The loudspeaker 14 is disposed outside the housing of the main terminal 11 and is connected electrically to the main terminal 11 via an electrical cable 141. The main terminal 11 enables the loudspeaker 14 to generate an acoustic output corresponding to the wireless incoming signals from the mobile telephone unit (T). The microphone 13 is connected electrically to the main terminal 11 via an electrical cable 131 and supplies to the main terminal 11 the wireless outgoing signals that are to be provided to the mobile telephone unit (T). Since it is necessary for the microphone 13 to pick up sounds coming from the mouth of the driver, the microphone 13 is typically installed on the driver's clothing or at a sun visor adjacent to the roof of the car.
The drawbacks of the conventional apparatus 10 are as follows:
1. The conventional apparatus 10 is inconvenient to install. It is difficult to mount the main terminal 11 within the passenger room of the car at a position in front of the driver because of crowded conditions thereat. In addition, the various electrical cables 121, 131, 141 which interconnect the plug 12, the microphone 13 and the loudspeaker 14 to the main terminal 11 are an eyesore because they cannot be conveniently concealed.
2. If the microphone 13 is installed at the roof of a car, reception is likely to be relatively poor since the microphone 13 easily picks up noise and other interference. The quality of the sound picked up by the microphone 13 is enhanced when the latter is installed on the driver's clothing. However, the range of movement of the driver is severely limited by the electrical cable 131 which connects the microphone 13 to the main terminal 11. In addition, the electrical cable 131 is always subjected to tension, thereby affecting adversely the service life of the same.